Within the last decade, an amount of literature has been published describing various polycrystalline, microcrystalline, or non-vitreous fibers and other shaped articles of refractory metal oxides. These articles are made by various non-melt processes, such as by drying films of solutions of oxygen-containing metal compounds, or drying organic polymeric bodies, such as cellulose or rayon, impregnated with such a solution, or by extruding and drawing, or spinning, viscous fluids of such metal compounds into fibers. The articles are then heated to remove water, organic material, and other volatile material to produce refractory articles.
Art in the area of polycrystalline inorganic fibers includes British Pat. No. 1,287,288, U.S. Pat. Nos. 3,385,915, 3,632,709, 3,663,182, 3,846,527 and the art cited in U.S. Pat. Nos. 3,709,706 and 3,795,524. Oxide fibers other than those identified as fiberglass are still in the relatively early stage of development.
In many technologies, there is a need for a relatively inexpensive continuous refractory fiber product with desirable physical properties, such as high strength, high heat emissivity, high modulus of elasticity, chemical resistance, and the retention of such properties after exposure to high temperatures beyond the capability of presently commercially available fiber materials.
U.S. Pat. No. 4,010,233 broadly discloses inorganic fibers comprising a metal oxide phase and a finely divided carbon dispersed phase. There are no examples drawn to alumina-silica fibers containing carbon as the dispersed phase or to the superior stability in an oxidative atmosphere provided by such fibers. The patentee states that mullite fibers which did not contain SiC disintegrated into dust when touched (col. 21, lines 34-36).